Lifting jack



Mar. 3, 1925.

1,528,236 W. G. ARMSTRONG LIFTING JACK Filed March 2, 1.922 2 sheetsshefi 19 F-W57 'INVENTOR.

HALTER AEMSTPON ATTORNEY.

w. s. ARMSTRONG Mir.

LIFTING JACK I Filed March 2, 1922 2 Sheets-Sheet 2 ATTORNEY.

*INVENTOR.

Nurse 6. Aensr ouq.

Patented Mar. 3, 1925.

UNITED STATES PATENT OFFICE.

WALTER G. ARMSTRONG, OF BRIDGEPORT, CONNECTICUT, ASSIGNO'R TO THE AMERI-CAN TUBE & STAMPING COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORA- TIONOF CONNECTICUT.

LIFTING JACK.

Application fi1ed.March 2, 1922. Serial No. 540,494}

To all whom it may concern: 1

Be it known that I, WAIJ1ER G. ARM- STRONG, a citizen of the UnitedStates, residing at Bridgeport, Connecticut, have invented certain newand useful Improve type and the leading object of my present inventionisto improve upon the constructions of said applications by simplifyingthe construction of the jack and reducing the number of parts. A furtherobject of my invention is to provide a better and more effective springaction for actuating the pawls. 7

Further objects, and objects relating to details and economies ofoperation and con struction, will definitely appear from the detaileddescription to follow. plish the objects of my invention, in oneinstance, by the devices and means described in the followingspecification. My invention is clearly defined and pointed out in theappended claims. A structure constituting a preferred embodiment of myinvention is illustrated in the accompanying drawings, forming a part ofthis speclfication, in

which Fig. l is a side elevation of my improved jack, the operatingmechanism being shown in dotted lines.

Fig. 2 is a sectional view on anenlarged scale through the upper part ofthe jack, showing the spring set for lowering movement.

Fig. 3 is a perspective view of one of the pressed metal pawls used inthis jack, and

Fig. 4 is a sectional view similar to Fig. 2 of a modified construction,showing the spring set for raising.

I accom In the drawings, the same reference numerals refer to the sameparts throughout the several views.

The form of lifting jack disclosed in my pending applications, comprisesa casing, a rack 's-lidably mounted in the casing, an operating leverpivoted in the casing, and a pair of pawls adapted to engage the teethof the rack. One of these pawls, the lifting pawl, is pivoted on theinner end of the operating lever and the other, the holding pawl ispivoted on a pivot fixed in the casing. A spring is provided, the endsof which extend through perforations iii the back walls of the pawls andthe action of the jack is reversed by shifting the center of the springfrom one side to the other of a straight line connecting saidperforations. When the center of the spring is nearer the rack than theends of the spring, said ends yieldingly force the pawls into engagementwith the rack and the parts are in raising position. 'When the center ofthe spring is further from the rack than the ends, said ends tend towithdraw the pawls and the parts are in position for lowering movement.In said construction, the shifting of the spring is effected bya pivotedreversing lever and a link connecting a central part of the spring withsaid reversing lever.

My present invention consists in eliminating the link and using aspecially formed spring, the central portions of which extend rearwardlyand connect directly to the reversing lever. One important feature of mypresent invention consists in a special, double-armed spring connecteddirectly to the reversing lever. Each arm of the spring may be ofright-angled formation so that'the portions which take the place of thelink, used in my prior constructions, are a part of the spring arms andthe effective length of the spring arms is correspondingly increased.

lower end of the casing are welded to the base plate, 13. I provide apair of sideplates, 14, which are welded to the sides of casing, 10, andwhich have the feet, 16, welded to the base-plate. These side-plates maybe pressed inwardly, at '15,. to lie agaji'n'stthe portions, 11, of thecasing.

The channel-shaped rack, 17, is slidably mounted in the channel of thecasing and has a plurality of teeth, 18, struck out from its base. Ahead, 19, is mounted on the upper end of said rack. A reinforcingcollar, 20, is mounted on the upper end of the casing and has a tongue,21, which extends within the channel of the rack and prevents dust anddirt from entering the interior of the casing.

A retaining pawl is pivoted in the casing on the pin, '22. Since theretaining and lifting pawls are identical, we shall use the samereference numerals in describing them. Each of these pawls comprises theparallel, spaced side walls, 23, connectedby a front wall, 24;, thelatter having a slot, 25, formed centrally therein. A tongue, 26, isstruck laterally from the rear edge of one side wall and forms a sort ofbridge extending beween the rear edges of the side walls, 23, andkeeping them spaced correctly. This ear, 26, is perforated, at 27, toprovide a bearing for one end of the spring. Cain surfaces, 28, areformed on the rear edges of the side walls for a purpose to be describedhereinafter.

The operating lever, 29, has its rear end formed into a socket, 30, to,receive the handle, 31. This lever is pivoted in the casing on the pin,32, and the forward end, 33, of the lever, which extends into thecasing, carries a pivot pin, 34, on which the lifting pawl'is pivoted.The end, 33, of the lever extends between the side walls, 23, of thelifting pawl. The casing has a cam surface, 43,- which cooperates withthe back of the lifting pawl, as will be more fully set forthhereinafter.

A wire spring of special double-armed form is provided for actuating thepawls. Each arm of this spring is of substantially right angle form, asshown in Fig. 2, consisting of the rearwardly extending portion, 35, andthe vertically extending free end, 36. The central portion of the sprinat the rear ends of the portions, 35, is bent to form the loop, 37,which engages the pin, 38, on the reversing lever, 39. The free ends ofthe springextend through the perforations, 27,01? the lifting andretaining pawls, respectively, and bear against the ears, 26, at saidpoints. The reversing lever, 39, is. U- shaped and has one leg extendinginto the casing and pivotally connected with the rear end of the springby the loop, 37, and the other leg extending along the outside of thecasing and terminating in the finger grip,

41. The reversing lever is pivoted on the casing on the pin, 40. Theouter leg of the reversing lever engages the stop lug, 4L2, pressed outfromthe side wall of the portion, 11, of the casing.

The construction shown in Fig. 4: is identical with that just described,except for the formation of the spring. In this modified construction,the spring, 44, has its central portion bent or twisted to form arearwardly extending shank, a5, having an eye, 416, which receives thepin, 38, by which the shank, 45, is pivotally connected .to the innerleg of the reversing lever, 39. The free ends of the spring, 4L work inthe perforations, 27, of the pawls, just as in the form previouslydescribed.

From the description of the parts given above, the operation of myimproved lifting jack should be readily understood. In Fig. 1, the partsare shownin the lifting position so that, when the handle, 31, is workedup and down, the rack, 17, will be raised to lift the load engaged byhead, 19. In this position, the. adjacent ends of the verticallyextending portions, 36, of the spring are nearer the rack than the endsengaging the pawls and such free ends, engaging the pawls at theperforations, 27, force the pawls toward the rack. As the handle, 31, isdepressed, the lifting pawl is raised carrying the rack with it, whilethe retaining pawl rides over a tooth of the rack and snaps intoengagement with the next lower tooth hen the handle, 31, is raised, therack is held fron'i-dropping by the retaining pawl, while the liftingpawl moves down, riding over a tooth of the rack and springing intoengagement with the next lower tooth. This operation is repeated at eachstroke of the handle. hen it is wished to lower the load, the reversinglever, 39, is shifted to the position shown in Fig. 2. This shifts thespring so that the adjacent ends of the vertically extending portions,36, of the spring are further from the rack ,tnan the free endsof suchportions and, consequently, the spring tends to move the pawls away fromthe rack. This tendency is ineffective as long as there is a load on thepawl. In Fig. 2, the handle is lowered and the spring arm has withdrawnthe retaining pawl from the rack. As the handle, 31, is raised thelifting pawl is lowered and the load causes the rack to drop with saidpawl. Toward the end of the upstroke ofthe handle, the lower end of thelifting pawl engages the cam surfaces, 28, on the back of the retainingpawl and forces the latter into engagement with the rack, so that. thedownward movement of the rack is halted and the load is shifted from thelifting pawl to the retaining pawl. Vhen this takes place, the springHlIiVllJll: draws the lifting pawl from engagement with the rack. Now,the handle, 31, is de pressed and the lifting pawl, which is clear ofthe rack, moves upwardly. Toward the end of this movement, the back ofthe lifting pawl engages the cam surface, 43, of the easing and isforced by it into engagement with the rack so that, as its upwardmovement continues, it takes the load from the retaining pawl and thespring arm withdraws the latter from engagement with the rack. Thisoperation is repeated at each stroke of the handle. The operation of themodified con struction shown in Fig. 4 is the same.

The improved construction disclosed herein results in a simplificationof the jack since the spring is connected directly to the reversinglever and no link is used as in my prior constructions. Furthermore, thespring is anchored at the loop, 37, and both the rearwardly extendingportion, 35, and the vertically extending portion, 36, constitute a partof the spring arm, so that I have a longer spring arm and, consequently,a better and more effective spring action. It will be noted that theportions, 35, flex with respect to each other with a scissors-likeaction, when the spring is in action and that the entire spring arm fromthe loop, 37, to the free end of the spring flexes under pressure. Theform shown in Fig. 4 results in a simplification of construction byeliminating the link but the spring arm is not so long and the spring isnot so effective as the preferred form.

I am aware that the construction de scribed herein may be alteredconsiderably without departing from the spirit of my in vention and,therefore, I claim my invention broadly, as indicated by the appendedclaims.

Having thus described my invention, what I claim as new and useful anddesire to secure by Letters Patent is 1. i1 device of the classdescribed comprising a casing, a rack slidably mounted therein, anoperating lever pivoted on said casing, a lifting pawl carried by saidlever and engaging said rack, a retaining pawl pivoted on said casingand engaging said rack, a spring having its ends engaging said pawls andits central portion extending rearwardly, and a reversing lever directlyconnected to said rearwardly extending central portion.

2. A device of the class described comprising a casing, a rack slidablymounted there in, an operating lever pivoted on said casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and engaging said rack, a spring having its endsengaging said pawls and its central portion formed into a loop, and areversing lever pivoted on the casing and having a pin engaging in saidloop.

3. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted on said casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and engaging said rack, a spring havinga centralloop and a pair of spring arms extending first forwardly and thenvertically from said loop with the free ends of said arms engaging saidpawls, and areversing lever pivotally connected to said central loop.

a. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted on said casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and engaging said rack, a spring having a pair ofangular spring arms the free ends of which engage said pawls, and areversing lever connected directly to said spring at the junction ofsaid arms.

5. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted on said casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and engaging said rack, a spring having a centralloop and a pair of right-angled spring arms each extending forwardlyfrom said loop and thence vertically, and a reversing lever pivotallyconnected to said central loop.

6. A device of the class described comprising a casing, a rack slidablymounted there in, an operating lever pivoted on said casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and enga 'ing said rack, a spring having a pairof right-angled spring arms each including a horizontal and a verticalportion, the outer ends of said vertical portions engaging said pawlsand said arms crossing each other adjacent theinner ends of saidvertical portions, and a reversing lever connected to the rear ends ofthe horizontal portions of said spring arms.

7. A device of the class described comprising a casing, a load-liftingmember movable therein, an operating lever pivoted on said casing, alifting pawl carried by said lever and engaging said member, a retainingpawl pivoted on said casing and engaging said member, a spring having apair of angular spring arms the free ends of which engage said pawls,and a reversing lever directly connected to said spring arms.

8. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted on the casing, a liftingpawl carried by the lever and engaging the rack, a retaining pawlpivoted on said casing and engaging said rack, a spring having its endsengaging said pawls and its central portion formed into a shankextending laterally from the portions of the spring which engage the pawls, and a revel-sing lever pivotally connected to said shank.

9. A device of the class described comprising a casing, a rack slidablymounted therein, an operating lever pivoted 0n the casing, a liftingpawl carried by said lever and engaging said rack, a retaining pawlpivoted on said casing and engaging said rack, a

spring having its ends engaging said paw-ls and its central portiontwisted to form a rearwardly extending shank, and a reversing level'directly connected to the rear end of said shank.

In testimony whereof, I affix my signature.

WALTER G. ARMSTRONG.

